Method of level control for continuous casting



J. WOODBURN, JR

METHOD OF LEVEL CONTROL FOR CONTINUOUS CASTING w wzqibu 9f 35 Nov. 29, 1966 J. WOODBURN, JR 3,287,773

METHOD OF LEVEL CONTROL FOR CONTINUOUS CASTING Filed Dec. 5, 1963 8 Sheets-Sheet 2 2 4 I291 86 EI (i i In D 84 2 89 8 0- |:F O B B James AZ/0046400? J)? Xsfl 5 Sheets-Sheet 5 J. WOODBURN, JR

Nov. 29, 1966 Filed Dec.

United States Patent Ofiice 3,287,773 Patented Nov. 29, 1966 3,287,773 METHOD OF LEVEL CONTROL FOR CONTINUOUS CASTING James Woodburn, Jr., Wheaten, Ill., assignor t Amsted Industries Incorporated, Chicago, 11]., a corporation of New Jersey Filed Dec. 3, 1963, Ser. No. 327,642 4 Claims. (Cl. 22200.1)

The present invention relates to continuous casting.

The invention relates more particularly to continuous upcasing involving pressure pouring wherein a mold having a bottom pouring opening is associated with a ladle, and pressure is imposed on the molten metal in the ladle for forcing it upwardly into and through the mold.

It is, of course, desired to maintain the flow or movement of the molten metal into the mold at a certain predetermined rate to accommodate withdrawal of the cast product at a similarly constant rate. In this operation, it is desired to maintain the molten portion of the metal in the mold at a certain height relative to the freezing and casting function therein. As the cast article is withdrawn continuously, it tends to lessen the height of the molten portion of the metal in the mold, but the air pressure imposed on the molten metal in the ladle forces the molten metal into the mold and tends to raise that height, that height under ideal conditions remaining constant.

A broad object of the invention is to provide novel means for sensing the change in level of the molten metal in a ladle to enable the operator to perform corresponding manipulations, such as additional pouring, or to perform other functions and controls, either manual or automatic.

A more specific object is to provide means for sensing such level by sensing the weight of the molten metal.

Still another object is to provide a novel method of casting of the character set out above.

Other objects and advantages of the invention will appear from the following detailed description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a vertical sectional view of casting apparatus embodying the principles of the invention, certain portions thereof such as the controls being shown diagrammatically;

FIGURE 2 is a face view of one form of indicating device utilized in the apparatus;

FIGURE 3 is a side view of the apparatus of the instrument of FIGURE 2;

FIGURE 4 is a diagrammatic view of one form of control device;

FIGURE 5 is a diagrammatic view of another form of control device; and

FIGURE 6 is a vertical sectional view of a modified form of casting apparatus.

Referring-now in detail to the accompanying drawings, attention is directed first to FIGURE 1 which includes a tank 10 including a receptacle 12 and a cover 14 detachably mounted thereon in sealing relation thereto to confine air pressure in the tank. The detailed structure of the tank may be as desired. A ladle 16 is mounted in the tank on load cells 18 which are weight sensing means, functioning to sense the weight of the ladle for use in conjunction with corresponding indicating means. As will be described more fully herein below, the weight of the ladle and the molten metal therein can be utilized for indicating the quantity of molten metal therein by subtracting the empty weight of the ladle from the gross weight sensed by the load cells. The ladle 16 may be of conventional form, made of insulating refractory material and, if desired, may have an induction heating coil 20 embedded in the wall therein for heating the molten metal 22 or maintaining it at a heated temperature.

The ladle 16 may be inserted in the tank receptacle 12, after the removal of the cover 14 therefrom, by suitable means such as a crane, after which the cover is replaced and sealed on the receptacle. The cover 14 is incorporated in an assembly 24 which includes a pouring tube 26 and a mold 28. The tube 26 is mounted in the cover by suitable means in sealed relation thereto, and it extends downwardly into close proximity to the bottom of the ladle. The tube extends to and communicates with the mold, the mold having a central passage 30 therein forming a cavity. This passage or cavity, as will be noted, opens through both the bottom and top of the mold, the molten metal being forced into the mold through the bottom and the cast product being withdrawn upwardly therefrom through the top opening. Preferably, the inner diameter of the pouring tube is equal to the diameter of the cavity.

The mold 28 includes a sleeve 32 forming the cavity which may be of such material as graphite. Surrounding the sleeve is a cooling jacket 34 of suitable high heat conducting material such as copper, and having an annular space 36 therein for circulation of cooling medium such as Water. This cooling medium may be injected through an inlet pipe 38 from a supply source (not shown) and ejected through an outlet conduit 40.

The cast product here indicated at 42 is in the form of a tube or pipe, and to produce such tubular product, the product is withdrawn at a predetermined rate relative to the rate of flow of the molten metal into the mold, together with other factors, e.g., temperatures involved. The cast product, after initiation of its removal, is continuously withdrawn by friction rollers 44 engaging it and rotating in the directions indicated.

The molten metal 22 is forced upwardly through the pouring tube 26 by air pressure produced in the sealed tank 10. It will be understood that for a given pressure the molten metal Will stand at a given level in the mold, and as the cast product is continuously removed, the level of the molten portion of the metal tends to lower and would lower if the pressure should remain constant. In order, therefore, to continue the pouring operation, additional pressure is produced in the tank, to maintain the level of the molten metal in the mold, because as the molten metal in the tank is depleted and the level thereof lowers, maintaining the level of the column in the mold is equivalent to raising the height of the column, i.e., the height of the column above the level in the ladle increases; hence the greater air pressure.

Air is introduced into the tank from a suitable source (not shown) through an inlet conduit 46 which includes a throttling control valve 48 of known type. Air is exhausted from the tank through an outlet conduit 50 having a control valve 52 therein of suitable and known type. The valves .48 and 52 may be controlled manually when the apparatus -is under manual operation, and controlled automatically When the apparatus is under automatic control, as described below.

As indicated above, the load cells 18 sense the weight of the lad-1e and the contents thereof, or the molten metal therein. This sensing operation may be utilized for use in any of a variety of different functions or control manipulations. In the simplest form of the operation of the apparatus, means is utilized for indicating the weight of the ladle as sensed by the load cells, and the operator performs operations in accordance therewith. The load cells are so constructed, and the indicating means so calibrated, as to indicate the weight of the molten metal in the ladle as a resultant of effectively deducting the empty weight of the ladle from the gross weight sensed and thus indicate the quantity thereof. This indication made by the visual indicators enables the operator to determine or whether to continue pouring, for example, or to replenish the molten metal, etc. For example, the operator knows the quantity of metal required for a single pouring operation, and if the visual indicating means indicates that sufficient molten metal remains in the ladle for that purpose, he can effect such a pouring operation, while on the other hand when he notes that there is insutficient molten metal for that purpose, he will arrange for another and full ladle to be put in place.

Instead of providing merely visual indications for guiding the operator, the apparatus may be used for directly efiecting control operations in accordance with the conditions sensed. For example, the load cells 18 may be incorporated in an arrangement of control instruments for automatically performing the necessary or desired control operations, such as developing air pressure in the tank to raise the level of the molten metal in the mold directly proportional to the removal of the metal in the form of the cast article, whereby to automatically maintain the supply of molten metal in the mold at the desired level to enable withdrawal of the cast article at the desired rate. The principal consideration of the apparatus is that the weight of the ladle, and more specifically the weight of the molten metal therein, is utilized for determining the quantity of molten metal thereof to enable either such manual manipulations as stated or to effect any such automatic manipulations as are desired.

The load cells 18 may be in the form of mechanical scales, for example, and utilized with a visual indicator 60 (FIG. 2) in which a band or pointer 64 mounted on a shaft 66 sweeps over a dial 62 and in doing so indicates the weight and hence quantity of molten metal in the ladle.

In the case of automatic control of the apparatus, the control valves 48 and 52 are controlled respectively through suitable lines of communication 54, 56, which may be electrical lines or cables for controlling electric instrumentalities which, in turn, control the valves 48 and 52 in a known manner. The exact construction of the valves and their control means may be any of various kinds, whether electrical or otherwise, and may if desired be mechanically, pneumatically, or hydraulically controlled or operated, etc. All of these forms are well known, and may be selected according to the practical circumstances surrounding any given installation.

The source of control of the valves is an instrumentality 58 here designated simply a controller, itself controlled by the load cells 18. The controller 58 is of suitable type according to the character of the valves, such as electrical, mechanical, etc.

The instrument 60 is adapted for use in automatic control, as well as manual control. An arm 68 is mounted on a sleeve 70' having a hand knob 72 friction-fitted on the shaft 66 and normally rotated with it, but capable of being manually rotated relatively to the shaft, and thereby set thereon. The arm is in position for engaging electrical contacts 76 upon swinging of the arm upon rotation of the shaft. Upon engagement of these contacts, a circuit is established through wires 78 for controlling the control apparatus which may be a shuttingolf operation.

Automatic means for supplying additional air upon depletion of the liquid level may be of any suitable and known type. For example, in referring to FIGURE 4, an arm 80 is mounted on the shaft 66 for swinging movement therewith. The arm 80 is connected at one end with an electrical conductor 82, and its other end is positioned for successively engaging contacts 84 connected with conductors 86. The conductors lead to instrumentalities 88 which are pressure-sensitive devices operating on the basis that upon existence of a predetermined pressure, a control function will be performed. In the present instance, these pressure-sensitive devices 88 are connected with the interior of the tank so as to function in response to the pressure therein. As the arm sweeps in response to depletion of the molten metal in the ladle, as sensed through the load cells 18, they successively put into circuit corresponding ones of the pressure-sensitive devices. These pressure-sensitive devices thereupon control one or both of the valves 48 and 52 for maintaining the pressure in the tank at the valve controlled by the characteristics of the pressure-sensitive devices.

It will be understood that satisfactory operation may be achieved by controlling the air pressure in the tank in steps, and it need not be increased in infinite small increments, as it will be understood the steps may be in relatively small increments. Notwithstanding the foregoing, it is also contemplated within the scope of the invention that gradual or infinitely variable control devices may be utilized, as indicated above, instead of the apparatus illustrated in FIGURE 4. Such arrangement may include, for example, a progessively advancing device such as the rheostat 88 of FIG. 5, or a coil and armature movable therein, or other pneumatic, hydraulic, or mechanical devices.

The foregoing tank and ladle apparatus is designed for batch type of operation. However, the invention is sufficiently broad to cover continuous replenishment. This may be done through a filling tube 90 which is mounted in the cover 14 and extends down to a point adjacent the bottom of the ladle. This pouring tube is at least as high as the top of the mold. The molten metal rises in the filling tube to substantially the same height as that in the mold, and in the normal operation the metal does not flow out of the filling tube in response to the air pressure produced in the tank. As the molten metal is depleted in response to the casting operation, and in the absence of replenishment, the air pressure in the tank is increased in the manner described above. However, it is possible to continuously replenish the ladle by pouring into the filling tube, and in this case the air pressure may be maintained constant and the rate of filling is controlled so as to maintain the level in the mold at the desired height. It is also possible to utilize a combination of the functions, namely control the air pressure for maintaining the desired height in the mold without filling, and then when it is desired to replenish the ladle, such may be done through the filling tube and in this operation the value of the air pressure is controlled to compensate for the filling operation to maintain the level constant in the mold.

While I have disclosed certain preferred forms of the invention, it will be understood that changes may be made within the scope of the appended claims,

I claim:

1. The method of continuous casting in conjunction with a sealed tank, a ladle and a mold, comprising the steps, developing air pressure in the tank and forcing molten metal from the ladle into the mold, sensing the amount of molten metal in the ladle, and developing air pressure in the tank in inverse proportion of the amount of molten metal in the ladle.

2. The invention set out in claim 1 wherein the sensing function includes sensing the weight of the ladle and the molten metal therein.

3. The method of continuous casting in conjunction with a sealed tank, a ladle, a mold, and means com'municating between the ladle and the mold, comprising the steps, developing air pressure in the tank, and thereby forcing molten metal from the ladle into the mold, freezing the molten metal in the mold, continuously withdrawing the article so frozen and cast from the mold, and increasing the air pressure in the tank in proportion to the rate of removing the cast article.

4. The method set out in claim 3 wherein the step of increasing the air pressure includes so increasing it in proportion to the change of weight of the molten metal in the ladle.

(References on following page) UNITED STATES PATENTS Rossi 22-572 Brennan 22200.1 Carleton 2282 Sylvester 22-69 Deakins et a1. 2282 6 2,992,691 6/ 1961 Schneider 2,997,756 8/1961 Strom 2269 FOREIGN PATENTS 5 907,202 10/1962 Great Britain.

J. SPENCER OVERHOLSER, Primary Examiner. R. S. ANNEAR, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,287,773 November 29', 1966 James Woodburn, Jr.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

.Column 4, after line 21, insert the following paragraph:

The load cells 18 sense only the ladle and the molten metal therein below the level thereof, and not the column in the pouring tube. The air pressure in the tank is imposed on the ladle and the molten metal therein in all directions so that a pressure balance exists. As the level in the ladle lowers, the column in the pouring tube thereabove, which increases, is not sensed by the load cells, the weight of this column reacting through the metal in the ladle which in turn produces back pressure on the air in the tank. The differential in air pressure as determined by the level in the ladle is proportioned to the height of the column in the pouring tube above the level in the ladle.

Signed and sealed this 12th day of September 1967.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J BRENNER Attesting Officer Commissioner of Patent 

3. THE METHOD OF CONTINUOUS CASTING IN CONJUNCTION WITH A SEALED TANK, A LADLE, A MOLD, AND MEANS COMMUNICASTING BETWEEN THE LADLE AND THE MOLD, COMPRISING THE STEPS, DEVELOPING AIR PRESSURE IN THE TANK, AND THEREBY FORCING MOLTEN METAL FROM THE LADLE INTO THE MOLD, FREEZING THE MOLTEN METAL IN THE MOLD, CONTINUOUSLY WITHDRAWING THE ARTICLE SO FROZEN AND CAST FOR THE MOLD, AND INCREASING THE AIR PRESSURE IN THE TANK IN PROPORTION TO THE RATE OF REMOVING THE CAST ARTICLE. 